Electric generator and regulator



Feb. 18, 1958 w. KOBER ELECTRIC GENERATOR AND REGULATOR 5 Sheets-Sheet 1Original Filed March 21, 1951 ATTORNEY) Feb. 18, 1958 w. KOBER I2,824,275

ELECTRIC GENERATOR AND REGULATOR Original Filed March 21, 1951 5Sheets-Sheet 2 4 ,7 A /f fl/ s R 6% 1 1g. 6.

' INVEN TOR. W/W/a/fl Haber BY A T TORNE Y5 Feb. 18, 1958 w. KOBERELECTRIC GENERATOR AND REGULATOR 5 Sheets-Sheet 3 Original Filed March21, 1951 Fig.1 1.

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p, W m I T MW/am Haber w yv Feb. 18, 1958 w. KOBER 2,824,275

ELECTRIC GENERATORANDREGULATOR Original Filed March 21, 1951 5Sheets-Sheet 4 Fig.12.

INVENTOR. BY W/fl/a/n Kober QMZA QM.

Feb. 18, 1958 w. KOBER 2,824,275

ELECTRIC GENERATOR AND REGULATOR Original Filed Mal ch 21, 1951 5 Sheets-Sheet a Fig.15. K 2 j v 43 Fig.16.

IN V EN TOR.

VIM/mm K019 ATTORNEYS 2,824,275 ELECTRIC GENERATOR AND REGULATOR WilliamKober, Fairport, N. Y.

Continuation of application Serial No. 216,713, March 21, 1951. Thisapplication June 29, 1956, Serial No. 595,572

14 (Ilaims. (Cl. 322-'-27)' This application is a continuation ofapplication Serial No. 216,713, now abandoned, filed March 2 1, 1951.

In my copending applications, Serial Nos. 216,185, now Patent 2,719,931,granted October 4, 1955, and 217,799, now Patent 2,784,332, grantedMarch 5, 19 57, the general methods of constructing a permanent magnetalternator with an axial air gap, and the use of an adjustable axial airgap as a means for controlling the voltage of a permanent magnet orother type field has been described.

It is the object of this invention to provide means and structureswhereby an axial air gap generator will adjust itself to maintain itsterminal voltage substantially constant under varying loads.

It is another object to obtain said inherent adjustment to substantiallyconstant terminal voltage over a range of speeds of rotation.

It is another object to obtain said inherent adjustment to substantiallyconstant terminal voltage over a range of load power factors.

It is a principal object of the invention to provide means andstructures so that an inherent adjustment to' substantially constantterminal voltage will take place over a range of changes in load, andspeed, and load power factor applied together or in any combination. Themethods and structures that produce these and other objects of theinvention are set forth in the following specifications and drawings.

In the drawings,

Figs. 1 to 5 show the armature and field of a dynamo electric generatorof the type used in applying the invent'ion.

Fig. 6 is an axial sectional view of a generator showing the armaturemounted for resiliently resisted limited rotation in response to changeof torque;- Fig. 7 isan elevation of the armature but with the windingsomitted, and Fig. 8 is a sectional view of-the grooved support for thearmature.

Fig. 9 is' a sectional view of the generator showing a modified supportfor the armature.

Figs. 10 and 11 are respectively sectional and eleva tional views ofstill another modified support for permitting axial movement of thearmature.

Fig. 12 shows still another modification of the armature support.

Fig. 13 is a sectional view showing the rotor field member mounting onthe shaft for limited axial movement thereon; Fig. 14 shows one of'theflexure plates used in this mounting.

15 is an elevation partly in section showing a modified mounting for therotor field member, and

Fig. 16 shows dynamometer' structurein which both movable and stationarymembers carry windings.

Figs. 1-5 show the general construction ofthe rotor-3 and stator 1' in apermanent magnet generator usingv an axial air gap. Four poles areshown,- but the adaption tov any number of poles is obvious. Theslotslirr stator 1 provide a place for the winding, not shown. The

United States Patent 0 rotating field 3 contains magnets 5 and polepieces 4 facing the stator. The rotor turns on shaft 6.

There are several forces acting between the rotor and the stator, and anunderstanding of them is necessary to an understanding of the invention.

First, there is the force of attraction between the pole face and thestator across the air gap. This force is given by the formula:

where B is the flux density, and A the area involved. All quantities arein c. g. s. units. Since B is not always uniform at all points on thepole face, the term B is more accurately the mean square of B over thevariable flux density areas involved. To give an idea of the magnitudesinvolved, a 4 pole generator having a flux per pole of 600,000 lines,and weighing about lbs., will have a force of attraction between rotorand stator of 1,500 lbs.

The second force to be considered is that developed as an additionalattraction or repulsion by armature currents. When the armature currentis exactly in phase with the generated voltage, the poles formed on theface of the stator are displaced exactly 90 electrical degrees fromthose of the rotor, and each section where repulsion (N against N or Sagainst S) exists is balanced by an equal section where attractionexists (N against S). This is true of a polyphase winding in whicharmature reaction is constant in magnitude and moves smoothly inrotation exactly in step with the rotor field. When a polyphase systemhas an unbalanced load, or in a single phase generator, there arealternate attractions and repulsions, however, these average to zeroover a full cycle, so that, except for a tendency to produce vibrations,no resultant force exists.

Itsh'ould be noted here that for the load current to be in exact phasewith the generated voltage requires a power factor slightly less thanunity, and leading. A unity powerl fafctor load is in phase with theterminal voltage, but this lags the generated voltage because itcontains as a component the inductive drop in the synchronous reactan'ceof the generator, which always causes a lagging displacement. Thus, aunity power factor load produces in part the effects of departure inphase between generated voltage and load current to be discussedimmediately following.

If the armature current lags the generated voltage by 90, the polesformed on the armature directly oppose those of the field. This willproduce a force of repulsion, which can more clearly be understood interms of the resulting redaction in B, and the reduction in force thatfollows. It will be seen that this force depends greatly on a number ofspecific factors in the design of the generator If the armature currentleads the generated voltage by 90, the poles formed on the armatureassist those of the field.- A resulting force of attraction results.

The third force to be considered is a rotational force exerted on thestator by the rotor. Some amount of force exists even at no load,resulting from hysteresis and eddy current drag by the field on thestator, and from airfriction'across the small air gap. These forces arefairly small, however, and in addition relatively constant. A largerotational force results from the application of-a power drain to thegenerator output. This is most conveniently viewed as being the backtorque or power absorption by the stator which appears in electricalenergy. If the winding and associated losses in the generator as wellasthe output load are taken into account, this view is quite accurate.Assuming an ethciency of 90 percent (10% internal losses), the outputpower P in kw. and the rotational torque T on the stator are given bythe relation where n is the revolutions per minute. This equation isonly approximate, since at low power factors the internal lossesincrease, and the efficiency drops, so that the torque is not entirelyproportional to output power, but has some tendency to follow thecurrent value.

In a generator built according to Figs. l-5, the voltage generated inthe armature winding can be varied overa large range by a small changein the air gap. An increase in the air gap decreases the voltage, andvice versa.

By the methods of the invention now to be described, the forces aboveanalyzed can be used to produce motions of the armature which willaffectthe air gap in such a way as to oppose the change in voltagecaused by the load. In this way, these changes can be kept small.

When the load increases, the output voltage drops, so that the desiredmotion is such as to reduce the air gap. However, the force ofattraction between rotor and stator diminishes, and if the stator wereto be mounted on springs, the motion would be in the opposite directionto that desired. The torque on the stator, however, is quite large,usually representing a greater force at the mean armature radius thanthe change in attraction above noted. According to the invention, thestator is so mounted that this torque produces a motion tending to closethe air gap. This torque-produced motion is resisted by an elasticsupport, which is adjustable so that the degree of air gap, motion andhence voltage adjustment, is controlled to the desired value.

Figs. 6, 7 and 8 show one way in which this result can be realized. InFig. 7, four pins 8 are shown driven and anchored in the stator, andprojecting beyond it a suitable distance. Although four pins are shownfor purposes of illustration, any number from three up is obviouslyuseful. These pins fit into four angled slots 9 in the stator support10, which is in turn fastened to the housing 11. The slots 9 are bettershown in Fig. 8. The slots are closed at the front end to stop themotion of the stator before it can come in actual contact with therotor. They are open at the rear to permit easy assembly, but in workingposition the back plate 12 prevents the air gap from exceeding apredetermined maximum amount.

Springs 14 are fastened between pins 13 in the stator and 15 in the backplate, to restrain the rotary motion of the stator. The tension in thesesprings is adjustable .by rotation of the back plate 12, which ismounted so that it can be rotated and locked in a number of positions.By adjustment of these springs, the stator is so controlled that itsrotation is roughly'proportional to the torque on the stator. As thestator rotates, theslots slide it toward the rotor, reducing the air gapby the desired amount. i The slope of slot 9 is of importance insecuring the best results. Since the application of load reduces themagnetic pull of the rotor on the stator, producing through the inclinedplane action of the screw'8, 10 a tendency to rotate in the incorrectdirection, the torque must be given a definite mechanical advantage toovercome this. Since the change in magnetic pull is normally less thanthe torque force at the radius of the pins, any slope under 45 ispractical. As the slope is reduced, the rotary motion of the statorincreases.

It will be obvious that the direct engagement of pins 8 with the slots 9may be replaced'by a fully developed multiple thread, with the femalepart cut in 10 and the male part out in a collar in turn mounted tostator 1. The male and'female threads may alsobe interchanged betweenthese parts. This construction is illustrated in Fig. 9. To limit themotion of the stator, pin 17 isfitted into slot 16, which is of theproper angular width to V V 4 permit the desired motion. Flat or leafspring 15, adjusted by screw 18 develops a direct backward pull. In thisform, the spring force required depends on the pitch of the screw.Springs such as those shown in Figs. 6, 7 and 8 may also be used.

In Figs. 10-11 links 16 are used to give the relation between rotationaland forward motion. Each link has a spring 18 mounted to the moving endof the link from an adjustable anchorage 19. When links are used, anaxial beari g is sometimes advisable, as shown at 20, to prevent mistingand the resulting unbalance of the links.

Another method of support is shown in Fig. 12, where inclined planes 21fastened to the stator slide on matching planes 22 mounted on'the rotor.Here, it is necessary to use a spring 23 strong enough to overcome themagnetic attraction between rotor and stator as well as to supply theadded resistance which is overcome by the sliding on the inclined planeswhen the stator applies torque as the result of generator loading. Inthis form, the planes may be in direct sliding contact, or separated byballs or rollers. A pin 24 which tits in a slot in the part 22 limitsthe angular motion. j

In generators of the type to be used in the invention, the outputvoltage varies in proportion to the speed, all other factors remainingconstant. In a permanent magnet field generator, the proportion is verynearly direct. The torque compensation above described for loadvariations is not useful in controlling speed efiects. Such control isaccomplished according to the invention as follows:

In Figs. 13-14, the field structure 3 is shown, mounted on shaft 29 byfiexure plates 25 or similar devices permitting axial motion underspring resistance but maintaining a rigid alignment of the axis of 3with that of the shaft. Fly ball 26 and links 27 or other similardevices not illustrated but known in the art provide a forceproportional to speed, which is yielded to in proportion by fiexureplates 25. An additional spring 28 may be provided if needed. As thespeed increases, the weights 26 pull outward more strongly, pulling therotor away from the stator. A stop 30 is provided if otherwise thespring action would permit contact between rotor and stator at lowspeeds. By controlling the angle of the links 27 and the mass of weight26 it is possible to produce forces which greatly exceed the weight ofthe rotor, so that accelerations applied to the generator as a wholealong the axis will not produce any serious voltage fluctuations.

It is evident that both the torque and speed compensating motions can bebuilt into the rotor, and the stator fastened firmly in the ordinarymanner. Alternatively, the stator may be provided with a manualadjustment of axial motion to set the initial value of voltage. Thisform is shown in Fig. 15, where 31, 32 shows the shaft 39 threaded intothe rotor 3 using a screw thread of proper pitch, as already describedin connection with Figs. 6 to 15. Springs 40 and stop screw 41, whichlimit the possible angular motion are also similar in function tosprings 14 of Figs. 6 and 7 and screw 17 of Fig. 9. Part 33 is fastenedto the rotor 3 and bears on ring 34 which is under control of thesprings 35 and governor weight 36. Balls 37 are shown to minimizefriction, but'often a certain amount of friction is required here, toprevent oscillation of the rotor on'load surges. It will usually also beadvisable to cushion the ends of the slot in which the stop 41 fits, toprevent breakage by sudden changes of load. The form of Fig. 15, inwhich both load and speed adjustments take place in the rotor is simplerthan those in which the stator makes the load adjustment and the rotorthe speed adjustment. However, changes in speed of the driving meanswill produce inertial angular motions of the rotor with respect to theshaft, disturbing the voltage. This is not the case with the separatedcontrol function. I I

The combination of the'screw 31,. 32 andltlie" centrifugal device '35,3'6 will'a'ct to correctfor load and speed changes simultaneously, whenthe power factor of the load remains constant;

When the power factorvaries over'a widerange, additional force producingdevices are required'tocorrectfor the resulting voltage changes;

A generator having a substantially constant effective resistance R andsynchronousreactanceXmay be treated as a perfect source coupledtoits'output'through elements R and X in series. Generat'orsnot usingfieldcontrol, as those contemplated. in this invention, normally havesuch substantially constant values of R and Z. In standard vectornotation,

whereI is the component of I inphase with V, and I is the component of I90 degrees out ofphase with the lagging V. I

Multiplying a t +i( iz 5.-

The imaginary term (coefii'cient. of j) acts mostly, to rotate vector Ein respect to vector V, and has little. effect on its magnitude fornormal values of I I R and X. Hence, these may be ignored inpractice,whence This means that the drop in thegenerator E-V. (which is to bemade up byv voltage control) is the injphase current I times theeffective resistance-:R plusthe wattless current I times. the reactance;X. Hence, when the variable power factor loads. aretobe corrected for,which means differing values of I and I each term must be corrected forindividually.

Power. output is. given. by VI and: hence the. torque is proportional.to I since V is. substantially constant. Thus it is obvious that thetorque devices above described will take care of this drop when properlyadjusted.

To compensate for I X an added torque must be developed which isproportional to I Such a force can be developed by, for example,constructing an electrodynamometer in which the field coil develops aflux 90 out of phase with V, and the current coil a current in phasewith I, the load current. One form of such a device is shown in Fig. 16.Here part 42 is the field, and is stationary, while part 43 is movable,and is connected to the part it drives by link 46. Suitable devices notshown are provided to permit part 43 to move parallel to 42, and spacedonly a short distance from it, but without permitting actual contact.The winding 44 of the field coil is highly inductive, and if voltage Vis impressed across it, the resulting magnetic flux will be very closeto 90 lagging in phase behind V. Winding 45 of the armature 43 carriesthe load current I, either directly or through an intermediatetransformer. The force produced on 43 is then proportional to V1,, andhence to I A similar result can be obtained, in the form of rotarymotion, by using a standard universal series motor, reconnected asfollows: The field terminals are brought out and connected to thevoltage V. The field then replaces part 42 of Fig. 16. The brushterminals from the armature then carry current I, directly or through atransformer. The armature replaces part 43 of Fig. 16.

The pull developed by these dynamometers can be applied to the structureof Figs. 6, 7 and 8, for example by connecting link 46 of Fig. 16 to pin13 on the stator. If desired, a multiplying leverage can intervene tosecure the correct amount of force to eliminate the I X drop.

Another quite different method of securing constant voltage with a largerange of load power factors is to use a compensator (see U. S. Pat. No.2,526,671, dated 6 October 24, 1950, to William Kober). The'compensatoreliminates the effect ofload power factor on the output voltage. Theremaining'efiects of'loadand speedare then corrected by the structuresof Figs. 1 to 15, and as a result, substantial constancy of terminalvoltage under all possible operating conditions is maintained;

I claim:

1. In an electric generator having an armature, permanent magnet fieldproducing means, one of said armature and'said field producing meansbeing mounted for rotation about a predetermined axis, said armature andsaid field producing means being separated in the direction of said axisof rotation to define an axial air gap therebetween, and meanssupporting'one of said armature and said field producing means formovement relative to the other thereof along saidaxis'automatically'inresponseto variations in the torque force. betweensaid armature and said field producing means produced. upon varying theelectrical load on. said generator, said supporting means causing suchrelative axial motion to vary the length of'said air gap in a-directionto maintain the output voltage of said generator substantially constantdespite such changes in the'electrica'l loading thereof.

2. In an electric generator of: the axial air gap type having anarmature, field producing means, saidarmature and said field producingmeans'being separated to provide an airgap' therebetween, means mountingat least one of said armature and said field producing means formovement relative to the other thereof in response to torque changestherebetweenproduced by variations in the electrical load on thegenerator in a manner to. vary the length of'said air gap in a directionto maintain the generator terminal voltage substantially constant asthe. electrical load is varied, and elastic means resisting suchrelative movement.

3. Adynamoelectric generator of the axial air gap type having anarmature, rotating permanent magnet field producing means, an air gapseparating the working faces of said armature and said field producingmeans, and means supporting one of said armature and said fieldproducing means for movement toward and away from the other thereof tovary the length of said air gap automatically in response to variationsin the rotational force exerted on said armature by said field producingmeans upon increasing and decreasing the electrical load on thegenerator, said supporting means being so arranged that the length ofsaid air gap is varied in a direction maintaining the terminal voltageof said generator substantially constant with variations in theelectrical load thereon.

4. The generator of claim 3, wherein said supporting means includes pinand slot means.

5. The generator of claim 3, wherein said supporting means includesinclined plane means.

6. The generator of claim 3, wherein said supporting means includespivoted support link means.

7. In a dynamoelectric generator of the axial air gap type having anarmature, field producing means, and an air gap separating said armatureand said field producing means, means mounting one of said armature andsaid field producing means for rotation about an axis, and meanssupporting one of said armature and said field producing means formovement toward and away from the other thereof to vary the length ofsaid air gap automatically in response to variations in the torquetherebetween produced upon changing the electrical load on thegenerator, said supporting means causing such relative movement to varythe length of said air gap in a direction maintaining the generatorterminal voltage substantially constant as the electrical load thereonis varied.

8. A dynamoelectric generator having an armature, permanent magnet fieldproducing means mounted for rotation about an axis, said armature andsaid field producing means being separated in a direction along the axisof rotation of said field producing means to provide an axial air gaptherebetween, and mounting means for said armature including meansenabling rotation thereof about said axis automatically in response tovariations in the rotational force exerted on said armature by saidfield producing means produced by changes in the electrical load on saidgenerator, and means translating such rotation of said armature intomovement thereof along said axis relative to said field producing meansto vary the length of said air gap in a direction maintaining thegenerator terminal voltage substantially constant upon such changes inthe electrical load thereon.

9. In an electric generator, an armature, permanent magnet fieldproducing means, mounting means supporting said field producing meansfor rotation about an axis, and means supporting said armature formovement about said axis automatically in response to electrical loadproduced variations in the rotational force exerted thereon by saidfield producing means, such movement of said armature being in adirection to maintain the generator output voltage substantiallyconstant as the electrical load thereon is varied.

10. In a generator, a stator, a rotor mounted for rotation about anaxis, means supporting one of said stator and said rotor for rollingmovement along and about said axis toward the other thereofautomatically in response to changes in the rotational forcetherebetween produced by changes in the electrical loading of thegenerator, said supporting means causing such relative movement to varythe length of the air gap between said stator and said rotor in adirection to maintain the output voltage substantially constant, meansbiasing said one of said stator and said rotor toward the other thereof,and centrifugal force responsive means operable automatically inresponse to the centrifugal force produced by rotation of said rotor tomove said one of said stator and said rotor away from the other thereof,thereby to vary the length of the air gap therebetween in a directionmaintaining the generator terminal voltage substantially constant withvariations in the speed of rotation of said rotor.

11. In an alternating current generator, an armature, rotating permanentmagnet field producing means, said armature and said field producingmeans having working surfaces spaced apart along the axis of rotation ofsaid field producing means to provide an axial air gap therebetweemandsupport means for said armature including means causing the same to moverelative to said field producing means along said axis automatically inresponse to variations in the rotational force exerted on said armatureby said field producing means produced by changes in the electricalloading of the generator to vary the length of said air gap in adirection maintaining substantially constant the terminal voltagedeveloped by the generator. t

12. A generator as set forth in claim 2, together with means foradjusting the tension of said elastic means.

13. A generator as set forth in claim 3, wherein said supporting meanscomprise inclined plane means having a slope of less than forty-fivedegrees.

14. A generator as set forth in claim 7, together with stop meanslimiting the extent of such relative movement.

References Cited in the file of this patent UNITED STATES PATENTS614,608 Cantono Nov. 22, 1898 1,070,437 Ferguson Aug. 19, 1913 1,131,551Price Mar. 9, 1915 1,268,545 Chapman June 4, 1918 2,453,523 McCulloughNov. 9, 1948 FOREIGN PATENTS 25,245 Great Britain Oct. 8, 1898 172,387Great Britain Dec. 2, 1921

